External System in UML

Question

I am currently working on software requirements specification document, I am creating a use case to validate or communicate with external system, for example I a want to creating a use case that about sending notification emails to user outlook contacts, donI need to specified the detail for the external system? Like calidation or credentials?

Answer 1

Not in the UC diagram, but there are others where you might.

Use Case diagram

UC will show external systems that are involved in the UC as actors. The UC itself shows functionality of modeled systems and should no go to low with decomposition. Things like "communicate with external system" or "validate query" are not separate UCs but part of something broader like "Place an order". On this level you only show the main function, leaving details for other, more specific diagrams (e.g. activity diagram depicting the UC's flow).

Activity diagram

On activity diagram you show the information about processing but in general you do not show too much static data. As a result things like "Validate query" or "Create notification e-mail" will be separate actions within the activity. They may have be further decomposed as Activities with details about how validation is performed or what steps has to be performed to communicate with the system.

Sequence diagram

Sequence diagram is another great way of showing the flow of action, especially when communication between various parties (e.g. systems) is involved. Here you can show the order of messages being sent, to some degree actions taken (as called operations - so you can show that you run validation first and send the message to the e-mail system then if the validation was successful). With the operation you can also show information about parameters that has to be provided (so for example credentials for communication with external systems).

Other diagrams

It all depends on the specific diagram and most of them give you a possibility to show the other system in some way. Sometimes there is more than one good way to do so. Details would depend on what exactly you want to show and which diagram did you choose to present the information

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I would suggest you read some good books about modelling with the use of UML. Craig Larman's "Applying UML and patterns" or Howard Podesva's "UML for the IT business analysis" are my usual starting recommendations.